. >>> and this is what it takes to complete the tallest building in north and south america. we'll go to lower manhattan, where the final piece of the new one world trade center is being assembled as we speak. that's ahead on "cbs this morning." morning." >> announcer: this portion of "cbs this morning" sponsored by citi price rewind. buy now, save later. wants that pink castle thing. and you really don't want to pay more than you have to. only citi price rewind automatically searches for the lowest price. and if it finds one, you get refunded the difference. just use your citi card and register your purchase online. have a super sparkly day! ok. [ male announcer ] now all you need is a magic carriage. citi price rewind. start saving at citi.com/pricerewind. ♪ [spider-man] we got this. ♪ ♪ [mom] this hero stuff is easy! [ female announcer ] over every holiday season your mouth has been snacking, gift stacking nutcracking and yellowing. because if you're not whitening, you're yellowing. crest whitestrips remove over 10 years of stains, just in time for a white holiday. c